That last moment before impact

This coming Monday, NASA will broadcast its first attempt to modify the orbit of an asteroid, a capability that will be essential if we detect an asteroid that poses a threat of colliding with Earth. The planetary defense effort is focused on a craft called DART, for Double Asteroid Redirection Test, which will target a small asteroid called Dimorphos that orbits the larger 65803 Didymos, forming a binary system. If all goes according to plan, DART will direct itself to a head-on collision that slows Dimorphos, altering its orbit around Didymos…

…The planned collision will also be broadcast live on NASA’s YouTube channels. While we’ll know immediately whether the collision occurred as planned, it may take several months before we’re certain that Dimorphos’ orbit was successfully modified…

During its final approach to Didymos, DART will be distant enough that round-trip transmissions will take over a minute. As such, the final approach and targeting of the asteroid will be handled by an on-board navigation system called SMART Nav (Small-body Maneuvering Autonomous Real Time Navigation)…

As described by Evan Smith, DART’s deputy mission system engineer, the system will shift over to on-board navigation at about four hours before impact, and the SMART Nav will track the larger Didymos and use that for navigation until about 50 minutes before collision, or about a half-hour after it can be resolved. At 2.5 minutes prior to the collision, the ion engine will be shut off, and DART will coast into a collision at about 6 kilometers a second.

And then, if everything goes well, the transmissions will stop.

RTFA for all the geek details about the mission. Thoughts to be examined, resolved after the mission. Whatever time the Big Bang happens, I plan to be watching. Even though there is a small companion craft accompanying DART that will record the final encounter from (what we hope is) a safe distance. Slo-mo replays and all.